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Setting Core Data attribute to nil with NSBatchUpdateRequest(使用NSBatchUpdateRequest将核心数据属性设置为nil)

转载 作者：bug小助手 更新时间：2023-10-25 21:48:38 25 4
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Is it possible to set an attribute to nil using NSBatchUpdateRequest? Passing NSNull() to propertiesToUpdate isn't working:

是否可以使用NSBatchUpdateRequest将属性设置为nil？将NSNull()传递给PropertiesToUpdate不起作用：



let unlockRequest = NSBatchUpdateRequest(entityName: "MyEntity")
unlockRequest.predicate = NSPredicate(format: "self in %@", myObjectIDs)
unlockRequest.propertiesToUpdate = ["lockDate": NSNull()]
var error: NSError?
myContext.executeRequest(unlockRequest, error: &error)
if let error = error {
    log.error("Failed to unlock: \(error)")
}


I don't get any errors, but it doesn't clear the date.

我没有收到任何错误，但它没有清除日期。



I've also tried setting it to NSExpression(forConstantValue: NSNull()), but that doesn't work either (forConstantValue argument does not accept an optional value, so I can't pass it nil.).

我还尝试将其设置为NSExpression(forConstantValue：NSNull())，但也不起作用(forConstantValue参数不接受可选值，因此无法传递nil)。


更多回答

Did you try NSExpression(constantValue: nil) ?

您尝试过NSExpression(constantValue：nil)吗？

@Willeke Sadly it doesn't accept an optional value, so I can't pass it nil.

@Willeke遗憾的是，它不接受可选值，因此我不能将其传递为零。

@Sencha did you find a solution for this?

@Sencha你找到解决这个问题的办法了吗？

@Serluca No I never did, in the end I had to set my lock date to a date in the past to effectively invalidate the lock (acceptable for me but I'm sure not for other situations).

@SerLuca不，我从来没有这样做过，最后我不得不将我的锁定日期设置为过去的某个日期，以有效地使锁定无效(我可以接受，但我确定其他情况下不能)。

优秀答案推荐

Current API allows to pass nil as a constant value.

当前API允许将nil作为常量值传递。



unlockRequest.propertiesToUpdate = ["lockDate": NSExpression(forConstantValue: nil)]


This seems to work correctly in Objective-C:

这似乎在Objective-C中正常工作：



NSBatchUpdateRequest *batch = [[NSBatchUpdateRequest alloc] initWithEntityName:entityName];
NSExpression *value = [NSExpression expressionForConstantValue: nil];
batch.propertiesToUpdate = @{@"lockDate": value};
batch.resultType = NSUpdatedObjectsCountResultType;
NSError *error;                
NSBatchUpdateResult *results = [self.privateContext executeRequest:batch error:&error];


Old question but here is the way you do it in Swift, verified myself without any crash.

老问题，但这是你在SWIFT中做到这一点的方式，验证了我自己，没有任何崩溃。


// Or Optional<Date>.none as Any
unlockRequest.propertiesToUpdate = ["lockDate": Date?.none as Any]

更多回答

I can see that the method signature now accepts Swift optionals. If this is verified to work then that would be the problem solved! NSExpression.init(forConstantValue obj: Any?)

我可以看到方法签名现在接受SWIFT选项。如果这被证实是有效的，那么问题就解决了！NSExpression.init(forConstantValue obj：有吗？)

The compiler doesn't complain, but when I execute the request it throws an exception: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid string key (null) passed to propertiesToUpdate:'

编译器没有抱怨，但当我执行请求时，它抛出了一个异常：由于未捕获的异常‘NSInvalidArgumentException’而终止应用程序，原因是：‘传递给PropertiesToUpdate的字符串键(NULL)无效：’

The header for NSBatchUpdateRequest.propertiesToUpdate says: "The expressions can be any NSExpression that evaluates to a scalar value."

NSBatchUpdateRequest.PropertiesToUpdate的标头表示：“表达式可以是计算结果为标量值的任何NSExpression。”

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